There are a lot of varieties and styles of accordion in the world, and more than a few in France. But the stereotypical sound of an accordion in films about France ( almost always Paris) is bal muzette, like this old clip of Gus Viseur.

Muzette is an old word for bagpipes, and strangely enough that what was originally the hot sound. It was popular in the Auvergne, a mountainous rural region of France, and it was the poor auvergnats , who could work hard and live cheap, who came into Paris in droves in the late 1800's to rebuild the city along the plans of Baron Haussmann. They also had their own cafe's, and it was the cabrette that they liked to dance to. That sound was embraced by the gangsters, the apaches, and others and became the rage, around 1900. Here is sample of the most famous of the cabrettaires, Antoine Bouscatel. And yes, that bagpipe is actually tuned the way they liked. Soon after the rage for muzette, Italians began to arrive- like the guys from Auvergne, often looking for work. They brought with them accordions- the bi-sonoral or diatonic kind, that made a big sound and provided its own bass. There was a dispute between the two for a time. True fans of cabrette might smash an accordion on sight. But then there was a sort of story-book resolution: the daughter of Bouscatel took up with Charles Peguri, the son of the leading Italian accordion maker. There could have been fighting in the streets, but after some grumbling Bouscatel acquiesced to the marriage, in 1913, and Peguri began to play onstage with Bouscatel. Hearing the special tuning of the cabrette and the chords of the diatonic accordion together must have been a real challenge, but it caught on- and bal musette was created. And it changed. The cabrette drones were stopped, so the accordion bass could be better used. Then the cabrette was discarded, and accordion became the main instrument in a dance band- along with various other things, like banjo, upright bass, guitar, xylophone....whatever was thought handy. The bright and happy waltzes and polkas of the diatonic accordion were augmented by jazzier swing music and the mono-sonoral chromatic button accordion, and the music could be darker, with ambiguous titles like "Indifferance", and the accordion could accompany a femme fatale like Kiki of Montparnasse.

Besides the traditional polkas and walzes, there was also tango craze at about this time, and sometimes an Italian name was switched for Spanish, to foster the illusion that the accordionist was from Argentina, and the Peguri shop developed a chromatic version of the Argentine Bandoneon. Other dances that became popular were the java, a kind of staccatto mazurka, and the paso doble came in from Spain. And the later chromatic muzette accordion in the 1950's would evolve into a serious instrument in the hands of virtuosi like Marcel Azzola and , more recently, get less nostalgic and more daring in the composition of Richard Galliano, here playing his version of a famous piece by the guy at the top, Gus Viseur.